Aluminum alloy



' Patentedoch zll, i

' wns'ron mm, or

\ l mming. j

, UNITED, STA

PITTSFIELD,

mssacnusn'r'rs, assrenoa 'ro GENERAL mncrmc comm, A coarona'rrouor Newman I ALUMINUM mm The present invention relates to alumi- -num alloys but more particularly to aluminum alloy castings containing silicon and manganese with or without other metals.

It is an object of the 'present invention to provide a relatively cheap aluminum base alloy which: may be cast, have a. fair tensile strength, an elongation of approximately 1% in two inches, a low electrical c'onduc-' tivity, and a melting "point ibelow 800 C. An alloy of this character is suitable for use as the conducting bars and end rings in induction motor rotors.

The/alloy forming the subject matter 5f the present invention preferably consists of the following ingredients:

'l v I Per cent An @110 of this composition, a vol-'- ume conductivity of about 18% as 'compared with copper, 'a1tensile strength in the chilled-cast'stateof about 12,500 pounds per square-inch, an elongation-of about 1% in two inches and a melting point of about 7 80 The. alloy may be manufactured by melt- .ing the ingredients in a. suitable crucible,

for example a crucible made of magnesite ture is slightly above the melting point, silicon, manganese copper and magnesium .are added so as to give substantially the pro- 1 portions indicated above in the final prod or "graphite or cast iron the, interior of which is limed or'whitewashed'. The alumi'-.

numisfirst melted and when its tempera- -uct.; molten mass isvstirre'd occasionali sly until all the ingredients are melted. About 0.1%,of sodium is the'nadded to the dium.

' whatever.

Application niea February 4.1931. sewn in. 513,455. a

thorough dissemination of all the constituents and the molten metal: then poured into small pigs.

When employed for" casting motor rotors v the pigs may be remelted. in acast ironpot which has been thoroughly limed but prefmetalis allowed to stand for about five minutes before casting so as to allow all dross to arise to the surface and be removed and to allow the escape of all gases which may be present due to the sodium addition. The desired quantity of lhiilid molten metal is then--removed in a lad e and-poured into-a centrifugal casting'machine or is poureddirectly from the graphite crucible.

If the alloy is to be employed for chill casting, the sodium serves no useful pur. pose; 'However, in casting motor rotors, I have found it desirable to preheat the rotor 'erably in a graphite crucible. The molten to about, 600 C. before casting to ensure that the. alloy will completely fill the small conductorbars of the rotor. Underj such conditions, if thesodium is absent, the al-' loywill have a relatively coarse structure; The presence .of. sodium modifies this structure so that slow cooling-gives'the same ing will give: on an alloy containing no so- Aluminum allo s are usually modifiedwith sodium just fore casting. However, to simplify the manufacturing. process, I

final dispersed condition that chilled cool-'- prefer to add sodium to the alloy when itis [first made. The remelting' eliminates much of the sodium as dross but the original 0.1% provides suflicient excess so that enough sodium remains in-the final casting to accomplish.modification.' p

The present alloy may be employed for any general casting purpose which may require a 'light weight alloy of low electrical conductivity and not too great strength; The alloy may if desired be'cas't at slow speed in a centrifugal machine or with no rotation While man anese' aluminum alloys have beem employed heretofore in themanufacture of motor rotors, such alloys are not en tirely satisfactory since a manganese aluminum compound appears toseparate out inlarge cubes, throughout such metal thereby weakening it to a great extent. Silicon has approximately the same specific gravity as 5 aluminum" and, when. present in substantiallyequ'al quantities wlth manganese in an aluminum alloy, the silicon keeps the manganese 'in a 'finely dispersed-condition providing a fine grain uniform com osition in m which there is no segregationb the components in the cast product. V.

' While I prefer to employ an alloy containing about 8% manganese and 8% silicon with the remainder aluminum, my invention is not limited to-thesespecific quantities.

The'manganese and silicon are employed in substantially equal amounts which, foreach of these ingredients, may vary from about 4% to about 13%. The lower quantity of an silicon and manganese(4% each) provides an alloyhaving a-tensile strength of about 19,000 pounds per square inch and a conductivity of about 24.4%, while the alloy with'the higher silicon and manganese cones, tent (13% each) provides-an alloy having-a tensile strength of 10,500 pounds per square inch and a conductivity. of about 12.5%.

Although I usually employ in the alloy about 1% copper, 0.5% magnesium-and 0.1% :m. sodium, these ingredients are not absolutely essential. They afi'ect the physical properties of the alloy somewhat but may generally be omitted without adversely affecting its properties. If desired, the alloy may contain as; up to 4% copper. a The alloy may be strengthened and its elongation increased by the addition of a small amount of silver, for example 1%. The addition of silver has but little efi'ect on the electrical conductivity of the alloy, but

of course increases its 'cos What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An alloy containing about 8% manganese, about 8% silicon, the remainder of the alloy consisting substantiall of aluminum;

2. An alloy. containing rom 4 to 13% manganese, 4 to 13% silicon, the remainder 1 of the alloy consisting substantially of "';aluminum. I

' 3. 'An' alloy containing about 82.4% aluminum, about 8% silicon, about 8% mangan'ese, approximately 1% copper,- 0.5%

magnesium and 0.1% sodium.

'1 In witness whereof, I havev hereunto set my hand this 28th -day-,of J anuar 1931.

' v WESTON M BRILL. 

